The invention relates to a frame with a reception area for a plurality of vertically arranged circuit boards carrying electronic components, in which the reception area is provided on its top and bottom with an air inlet and air outlet and is closed in airtight manner on the other sides and is provided with a forced ventilation of the reception area by means of a blower system, with which a cooling air flow is produced from the air inlet to the air outlet.
As is known, such frames are used in large numbers in the modular construction of electronic equipment and installations. They are used on the one hand for mechanical reception and on the other for the electrical connection of assemblies and circuit boards, which are dimensionally matched to one another by predetermined grids or rasters and spacing steps. A standard format is the 19" system.
The dissipated heat produced by the electronic components on the circuit boards must be removed by cooling. For this purpose there is a through ventilation of the circuit boards by means of a ventilator arrangement, in that cool external air is sucked in and the heated air is discharged to the outside again. Thus, in the case of closed systems, there is a forced circulation by internal ventilators.
Frequently the ventilators are located in the rear wall of the frame and cooling air is sucked in by means of openings in the front of the frame. German Utility Model 87 13766 discloses such a frame, in which below the assembly reception area is provided a distributing area, which is connected to a front opening. Above the reception area is located an air collecting area, from which the heated air is sucked rearwards by means of an axial-flow fan and blown out. The height of the distribution area and the collecting area corresponds in each case to half one height unit, whilst the reception area or the circuit boards inserted therein is two height units of the 19" system. Particularly if the circuit boards are closely juxtaposed and therefore the gaps are small, the fact that the individual circuit boards are provided with a varying number of components means that on the one hand restricting constructions and on the other relatively large openings in the cross-sectional surface of the reception area. If, as in the known example, the distributor is too small relative to the reception area volume, the sucked in cooling air prefers to flow through those gaps having a wide cross-section, whereas the air flow in the constricted gaps is relatively small. Thus, there is an inadequate ventilation of the most densely equipped circuit boards, where the greatest amount of dissipated heat is produced.